RFR 8141457: keytool default cert fingerprint algorithm should be SHA-256

[Wang Weijun]

Hi All

Please review a code change at

   http://cr.openjdk.java.net/~weijun/8141457/webrev.00/

SHA-256 is now the default fingerprint algorithm, and MD5 is removed in the full list.

No new regression test, I consider the change trivial. If you think one is better, I'll add it.

Thanks
Max